Minor tumour shrinkage in nonfunctioning pituitary adenomas by long-term treatment with the dopamine agonist cabergoline.

Objective: The purpose of this study was to define safety and efficacy of medical therapy in the treatment of nonfunctioning pituitary tumours.

Design: We studied thirteen patients with a clinically nonfunctioning pituitary macroadenoma for response to cabergoline treatment for 1 year. Twelve/13 patients were already operated and had residual or recurrent tumours.

Methods: We determined the outcome of treatment by visual perimetry, computed tumour size measurement in MRI and hormonal response (changes in pituitary function, reduction of alpha-subunit).

Results: Seven/13 patients on cabergoline had a tumour shrinkage above 10% of the initial tumour volume. In 4 patients, this tumour shrinkage was correlated to an increasing distance of the tumour to the optic chiasm. Only 2/9 patients with visual field defects before therapy showed improvements in visual acuity under cabergoline. No significant side effects of the therapeutical regimens were observed. Neither LH and/or FSH expression in the tumour cells nor the reduction of the alpha-subunit serum levels by medical therapy was correlated to tumour shrinkage.

Conclusion: Given that these patients had advanced disease which makes it difficult to find significant therapeutic effects, medical therapy with potent dopamine agonists such as cabergoline may evolve as a novel therapeutic option in a subgroup of patients with clinically nonfunctioning tumours declining operation and radiotherapy.